1. Technical Field
The present invention relates to a vertical cavity surface emitting laser and an atomic oscillator.
2. Related Art
The vertical cavity surface emitting laser (VCSEL) is, for example, used as a light source of the atomic oscillator using coherent population trapping (CPT) which is one of the quantum interference effects.
In the vertical cavity surface emitting laser, a resonator generally has an isotropic structure, and accordingly it is difficult to control a polarization direction of laser light emitted from the resonator. JP-A-11-54838, for example, discloses a vertical cavity surface emitting laser which generates distortion in a resonator by a distortion imparting portion and causes double refraction to occur, so as to stabilize a polarization direction of laser light obtained by laser oscillation.
However, in the vertical cavity surface emitting laser disclosed in JP-A-11-54838, a lead-out wiring from an upper electrode has not been considered, and the upper electrode is provided so as to cover the entire upper surface including the distortion imparting portion, in a plan view. Accordingly, parasitic capacitance due to the upper electrode increases, and accordingly, characteristics of the vertical cavity surface emitting laser may be degraded. When the lead-out wiring is set thin in order to decrease the parasitic capacitance, a risk of peeling-off or disconnection at a portion with the great curvature of the lower surface of the lead-out wiring increases, and accordingly a yield ratio decreases.